[Scarebird]

I agree with HIS and Nick - the 455 breaks things and revving a motor with a 4 speed is where the fun is at.

[Bill Eveland]

Why stop at 4.25? Is a 4.5 stroke on a 4.120 bore really too much for a 389? 480 cid lower revving torque monster or is the bore/stroke/rod ratio really that bad?

[Half-Inch Stud]

Originally Posted by Nicks67GTO

Yes, the SD ported 290cfm KRE's.

Geez, that is going to be a SWEET "400"

Ah, just one more ting: What does SD say about 9.3:1 so you can press WOT on 87-to-89 Octane?

[Nicks67GTO]

Originally Posted by Half-Inch Stud

Geez, that is going to be a SWEET "400"

Ah, just one more ting: What does SD say about 9.3:1 so you can press WOT on 87-to-89 Octane?

I could ask them about that. I'm not sure what a 10.5:1 poncho would need for fuel requirements with a modern chamber, cool temps, and that stump puller. Its on a 112 l/s so it should technically be a little more forgiving and the good modern chambers don't usually require as much timing if i'm not mistaken, like maybe 32 degrees is all so that may play a factor too? I wonder if i could get away with some 89 or 90? Thats a good question to ask them regardless.

[Nicks67GTO]

Originally Posted by Scarebird

I agree with HIS and Nick - the 455 breaks things and revving a motor with a 4 speed is where the fun is at.

Agreed. I guess another part of my thinking was that an honest 500 ft/lbs of tq is completely unmanageable on street tires at WOT, will allow for donuts in a parking lot at any moment, and pull like a train everywhere in the power band. Dave from SD told me my TQ curve would be very flat and broad with the combo too. I don't see a downside to going with the 400 for a stick car really?

[PONTIAC LARRY]

With a 4 spd ...389-412 ci for these good reasons above.

[psw]

Originally Posted by TheCirque

I've got the 455 currently. It needs some love and money to run right. Is this where I should put my efforts?

If I'm puttin' together a motor for a 66 GTO...not numbers matching. And I'm looking for a driver, weekend cruiser. Is one of these motors going to lend itself to being more easily built, maintained and driven?

The ol' Jan and Dean song keeps runnin' through my head....."3 dueces and 4 speed, and a 389".

Part of me feels I'm not being very true to the GTO legacy with the 455. On the other hand, I want a healthy runnin' car.

Installing a bigger engine than "normal" is exactly the legacy of the GTO. In 64-66 it was the 389 into the mid-sized GTO. That has morphed into built 70's 455s into any GTO.

My '66 originally came with tri-power and the two-speed auto trans, which was long gone by the time I got the car in 1983. At that time it had a tired old stock 400ci-350HP engine from a '68 GTO and a TH350. I put a YC code 1971 455 block under the 400 heads in about 1985 and ran that for many years until I got tired of the continual fight against detonation (i.e. search for high-octane gas). Two years ago I put in a set of 6X-8 heads with about 9.5:1 and have been very happy with the combo for street/cruise/driver duty. It has a vintage E-brock P4B, a new E-brock AVS 800 cfm carb, stock replacement HEI, and a Comp Mag 280 cam. I know this is not the typical build discussed on this forum, but I have had good luck with these parts and I was able to put the combo together cheap with some parts I already had. Still using the TH350 mentioned above, but now with a 2500 stall converter.

Never had this combo to the strip or on a dyno, but I can vouch for the traction-limited behavior, once I got the tune right. I am running the original 3:55 limited slip rear end, stock suspension, with BFG T/A Radials 245/60-14s on the rear. You can smoke the tires anywhere in first gear, half way through second, and bark em good going into third. In first gear, the tires cut loose at about halfway into the primaries, before you even get to the secondaries. This is obviously not optimal for the strip, but the car is a blast to drive and cruise, it idles and starts with no problems. At least I will not waste the tranny this way, until I can get a stronger one in there and start optimizing traction. Took me a while to get it to run cool down here in Texas, but that can be solved, too, lots on this forum about that.

As previously mentioned in this thread, you can run tri-power if you want, and the 455 looks the same from the outside as the 389, so it can look as stock as you want it to. What's not to love? I think you would have to spend quite a bit more money to get the same performance out of a 389, including aluminum heads, roller cam, etc.

[Tim Corcoran]

Dave at SD performance will give you good advice and get you a great combo to meet your needs. Don't get confused with the many opinnions, go with "Super Dave".

[Tim Corcoran]

One of the disadvantages of a 455 is the massive torque. You pull up to a light along side of a 69 Camaro with a stout 350 and an out trans. You rev it up letting him know you want some action, you got a 455 and street tires and you smoke the tires so bad your going no where and you watch the Chevy leave you in the dust. Been there done that. If you run a stout 455 on the street you better have some big soft tires or all that torque will get you is tire smoke. I vote for the 400 for a street machine as it will have a better chance of hooking the tires up on the street. personally I hate looking at Chevy tail lights. I prefer looking at the headlights in the rear view mirror.

[psw]

Originally Posted by Tim Corcoran

Dave at SD performance will give you good advice and get you a great combo to meet your needs. Don't get confused with the many opinnions, go with "Super Dave".

I agree, if one wants to start from scratch, many of the builders on this forum are going to be able to please.

Notice that the thread diverged into a discussion about 4-sp 400s build by SD. The OP was about rebuilding an existing 455 in a 1966 versus going back to a 389. I was merely relaying my experience with the very same decision on a budget.

[GOAT WHORE]

No question, 455. Put that tri-power on it and let r rip!

[ta man]

Originally Posted by Nicks67GTO

I could ask them about that. I'm not sure what a 10.5:1 poncho would need for fuel requirements with a modern chamber, cool temps, and that stump puller. Its on a 112 l/s so it should technically be a little more forgiving and the good modern chambers don't usually require as much timing if i'm not mistaken, like maybe 32 degrees is all so that may play a factor too? I wonder if i could get away with some 89 or 90? Thats a good question to ask them regardless.

I'm running 85 cc chambers on a 462 with KRE heads and can run on 87 octane...Last friday I ran on a mix of 60%87 octane and 40% 91 octane .I'm at about 10.25 :1.

[A.W.Dille]

One of the best combo's I've seen belongs to a friend and fellow board member, Ducks Goat. He has one of the best running 455's in his 65 GTO that I've ever ran across. Street driven, pump gas, hyd flat tappet cam, KRE heads, RPM intake with and out of the box 830 Holley auto, trans and 3.55 gears. Runs solid quarter mile times of 11.66. Even though I've had a 455 once years ago and went back to a 400 in my GTO you can't deny the 455 set up properly will make the better street engine as long as you can get it to hook.

[ta man]

Originally Posted by Nicks67GTO

Agreed. I guess another part of my thinking was that an honest 500 ft/lbs of tq is completely unmanageable on street tires at WOT, will allow for donuts in a parking lot at any moment, and pull like a train everywhere in the power band. Dave from SD told me my TQ curve would be very flat and broad with the combo too. I don't see a downside to going with the 400 for a stick car really?

I'm a big believer in more cubes is better...but in this case I think this 400 build will be great.Anybody that has ever dealt with Dave at SD knows that this will be quite an engine....Nick is he building the complete engine?This should be a smooth nice running street engine when done....but it will still do what is described aboveWhat was Daves estimate on power?450hp/500ft/lbs

[Nicks67GTO]

Originally Posted by ta man

I'm a big believer in more cubes is better...but in this case I think this 400 build will be great.Anybody that has ever dealt with Dave at SD knows that this will be quite an engine....Nick is he building the complete engine?This should be a smooth nice running street engine when done....but it will still do what is described aboveWhat was Daves estimate on power?450hp/500ft/lbs

500-525hp and 500 ft lbs

[Nicks67GTO]

Originally Posted by ta man

I'm a big believer in more cubes is better...but in this case I think this 400 build will be great.Anybody that has ever dealt with Dave at SD knows that this will be quite an engine....Nick is he building the complete engine?This should be a smooth nice running street engine when done....but it will still do what is described aboveWhat was Daves estimate on power?450hp/500ft/lbs

oh and ill be building it myself. I already have some of the parts, the rest i intend to buy from him. Ill get the machine work done locally and me and an old buddy will do the assembly/startup.

[Nicks67GTO]

BTW sorry for hijacking the heck out of this thread....

[Half-Inch Stud]

Originally Posted by A.W.Dille

One of the best combo's I've seen belongs to a friend and fellow board member, Ducks Goat....Street driven, pump gas, hyd flat tappet cam, KRE heads, RPM intake...830 Holley auto, trans and 3.55 gears...quarter mile times of 11.66. ....

TH400 = auto. Do not pass go. Nor collect $100. You're back at Post #15.

[ta man]

Originally Posted by Nicks67GTO

BTW sorry for hijacking the heck out of this thread....

Oops I thought you were the original poster...

[A.W.Dille]

HIS, forgot to put the comma in between the Holley and auto trans. It was a long day.